IRAQ hostage Kenneth Bigley last night begged Tony Blair to help save his life, saying: "You are the only person now on God's earth that I can speak to."

In a dramatic video released by his kidnappers, the 62-year-old from Liverpool pleaded with the Prime Minister to "show compassion" for his plight..

Four hours later, Mr Bigley's family appealed to the extremists to show mercy and spare his life. His son, Craig, 33, said: "You have proved to the world that you are committed and determined. We ask you as a family to be all-merciful."

The harrowing footage of his father, released on the internet by followers of terrorist Abu Musab al-Zarqawi, is the latest torment for the Bigley family and an open taunt to the British Government.

Looking pale and drawn, and with his hands bound behind his back, he said his wife would be unable to go on if he was murdered.

The footage appears to indicate Mr Bigley may have been granted a temporary stay of execution while his kidnappers await the response of the British Government.

Mr Bigley is being held captive by the extremist militant al-Zarqawi group, which is demanding the release of Iraqi women prisoners.

However, last night Foreign Secretary Jack Straw said Downing Street would refuse to negotiate with terrorists. He told reporters: "With reference to the appalling situation in which this evening the terrorists have placed Mr Bigley.

"Our hearts go out even more to him and his family, but I'm afraid to say that it cannot alter the position of the British Government."

A Downing Street spokesman said: "The Foreign Office is looking into it and is keeping Mr Bigley's family fully informed.

"We continue to do all we can to resolve the situation, but people understand how

difficult the situation is." In an earlier statement, the Foreign Secretary appeared to indicate hope was running out. He said: "We continue to do everything we can to secure Kenneth Bigley's safe release, but it would be idle to pretend that there's a great deal of hope."

He said the family were "preparing themselves for the worst" but stressed Britain could not get into a situation "where we start bargaining with terrorists and kidnappers", because he said "that would put many more people's lives at risk."

His two follow captives, Americans Eugene Armstrong and Jack Hensley, were both executed earlier this week.